1. Field of the Invention
The present invention relates to the field of equipment for reanimation and heart assistance. In more precise terms, the invention consists of a one-piece apparatus or satellite heart which is implanted surgically in the right hemithorax in order to assist the two ventricles of a diseased natural heart. This apparatus comprises two deformable-diaphragm pumps actuated by a compressed gas as well as means for connecting the pumps to the four natural blood vessels which communicate with the diseased heart.
2. Description of the Prior Art
The technique of cardiac transplantation in which a natural heart taken from a donor is grafted on a recipient has now been fairly well mastered and recent advances have resulted in an appreciable reduction of rejection phenomena. The practical application of this technique, however, remains relatively limited and fails to meet actual requirements by reason of the lack of natural heart donors.
For the reason just stated, it is an advantage to be able to assist the diseased heart of a patient by implanting a prosthesis in a patient's thoracic or chest cavity, this prosthesis being designed to operate in parallel with the natural heart which has remained in place, to assist the natural heart in its blood-pumping function and if necessary to perform a replacement function for any length of time in the event of failure of the natural heart.
Numerous examples of pumps for assistance of the left ventricle of the human heart are already known. The major disadvantage of this assistance technique is that it points to the additional need to assist the right ventricle.
Furthermore, the shape of left-ventricle assistance pumps which have already been developed is unsatisfactory from a physiological standpoint. Extrapolation of the techniques already employed to a left and right ventricle assistance pump would result in an apparatus which is even less physiological and therefore practically unimplantable in close proximity to the heart.
The aim of the invention is to produce a double cardiac assistance pump which is easy to use, which is efficient without giving rise to any serious disadvantage or inconvenience from the patient's point of view and which offers a high degree of reliability.
The cardiac prosthesis in accordance with the invention takes into account on the one hand the best location for implantation in the patient and on the other hand the best external shape which is compatible with this location and with a simple, effective and reliable technology of diaphragm pumps and connecting means.
The choice of the best location takes into account the following problems:
The overall size of the prosthesis with respect to the organs which are located around this latter. PA1 The size of the artificial blood vessels or tubing employed for connecting the prosthesis to the natural blood vessels. PA1 The ease of attachment of artificial blood vessels to the natural blood vessels and of connection to the prosthesis. PA1 The need to ensure that the prosthesis does not interfere geometrically with the beats of the natural heart. PA1 The pumps for assisting the right heart and the left heart are directly connected to the right auricle and to the left auricle by means of two artificial blood vessels (hose elements) which are extremely short since the satellite heart is placed next to the natural heart. PA1 The pumps for assisting the right heart and the left heart are connected to the bottom end of the pulmonary artery and of the aorta respectively by means of two parallel ducts or so-called hose elements which are continuously in contact on the one hand with each other and on the other hand with the external wall of the pericardium. Thus the volumes occupied within the chest cavity are very small and pressure drops within the artificial blood vessels are minimized. PA1 The shell in which said prosthesis is contained has a first substantially flat face adapted to bear on the patient's diaphragm and a second face located opposite to the natural heart and forming a substantially right-angled dihedron with the bearing face in the proximity of the ports, said second face being provided with two connecting ports, the shell being completed by a wall having a generally convex shape and provided with two other connecting ports which are inclined substantially at an angle of 45.degree. with respect to said bearing face. PA1 The prosthesis being placed horizontally on said first face and being viewed on said second face which is provided with the two ports for connecting said prosthesis to the auricles of the natural heart, said ports are so arranged that the port for connecting to the left auricle is located farthest to the right and that the port for connecting to the right auricle is located to the left of the port for connecting to the left auricle. PA1 Pumping of blood is performed in the case of each pump by deformation of pouches of flexible hemocompatible material containing the blood, said deformation being produced by the external mechanical action of a compressed gas supplied by a device located outside the prosthesis.
These conditions are satisfied by implantation of a prosthesis in accordance with the invention within the right hemithorax, that is to say between the muscular diaphragm and the right lung, and against the natural heart. The prosthesis proposed by the invention has a flattened and highly rounded general shape and is laid directly on the diaphragm. With respect to the human body, the satellite heart is symmetrical with the natural heart.
The symmetrical arrangement just mentioned is attended by the following consequences:
The ports for admission and discharge of blood in the two pumps are located on the prosthesis face which is opposite to the natural heart at suitable angles in order to facilitate connection of said ports by the medical practitioner and to prevent either the artificial or the natural blood vessels from being subjected to any bending stress, tensile stress or shearing stress.
Blood-circulating pumps are of the flexible diaphragm type and are actuated by a fluid commonly consisting of compressed air, nitrogen or argon. The diaphragms are formed of hemocompatible polymer and especially of polyurethane. The ports of the pumps which are rigidly fixed to the prosthesis envelope are fitted with means for quick-action coupling to the artificial blood vessels, thereby facilitating the delicate operation of air-purging of the prosthesis.